U.S. Pat. No. 4,894,012 and WO 89/04640 disclose a two-step procedure for producing fiber-reinforced dental appliances. First, a fiber-reinforced composite material is produced having the requisite stiffness and strength characteristics and thereafter a dental device is formed therefrom. The composite material comprises essentially a polymeric matrix and a fiber component embedded within the matrix. The materials employed are preferably fully polymerized thermoplastic materials. Restorations such as bridges are prepared by heating the fiber-reinforced composite material with a heat gun until soft and then forming the material using a dental cast. Finally, acrylic teeth are fixed thereto.
U.S. Pat. No. 5,098,304 discloses a method for reinforcing composite resin systems for restoring or splinting teeth which utilizes glass fiber material. Bridges are formed by first preparing the teeth which are adjacent to the missing tooth by grinding and then fixing a mesh or rope of fiber glass to the teeth. Thereafter a replacement tooth is formed on the fiber glass material.
U.S. Pat. No. 5,176,951 and WO 91/11153 disclose a method of reinforcing a resin portion of a dental structure, which comprises the steps of applying one or more layers of a light weight woven fabric made up of polyaramide or polyethylene fibers to a resin portion of a dental structure and covering the woven fabric with more of the resin. In this method the fiber material and the resin have to be combined by the user when preparing the dental restoration. This is inconvenient and bears the risk of forming air pockets which cause destabilization of the restoration.
WO 95/08300 relates to a method for manufacturing a dental prostheses wherein a preimpregnated fabric part is placed on a shaping model and formed on the model by compression. Then the organic matrix of the preimpregnated fabric part is cross-linked to obtain a rigid support shell and successive layers of organic resin are applied onto the support shell to form an external finishing coating. The support shell comprises between 20 to 60% by volume of fibers and other inorganic charges.
For producing fiber-reinforced bridges it is known to first prepare a dental cast which is partially covered with silicon to form a mould leaving a cavity for the restoration to be made. Then a preimpregnated fabric part is placed in the cavity, formed according to the model by compression and hardened. This process allows for the convenient preparation of metal free dental prostheses. However, the use of preimpregnated fabric parts with a high fiber content requires high pressure during compressing. In contrast, use of preimpregnated fabric parts with a low fiber content result in restorations with a limited stability.